A tetraphenylethene based polarity dependent turn-on fluorescence strategy for selective and sensitive detection of Hg in aqueous medium and in living cells

A turn-on fluorescent chemosensor strategy based on the change in the polarity of aggregation induced emission active tetraphenylethene is presented for the detection of Hg²⁺ in aqueous medium and in living cells. The sensing mechanism involves the formation of nonpolar fluorescent aggregates of tetraphenylethene molecules by elimination of polar moieties of TPE with Hg²⁺ interaction.     

Chromenone-rhodamine conjugate for naked eye detection of Al3+ and Hg2+ ions in semi aqueous medium

Chromenone-rhodamine conjugate 1 has been synthesized and its metal ion binding properties have been studied in CH₃CN/water (3:1, v/v; 10 mM HEPES buffer; pH = 6.85). Compound 1 senses multiple metal ions such as Al³⁺ and Hg²⁺ by exhibiting turn on fluorescence and color change (colorless to pink). Al³⁺ and Hg²⁺ ions have been distinguished with the aid of tetrabutylammonium iodide (TBAI). While in the presence of I^? the pink color of the 1.Hg²⁺ complex was completely discharged; under identical conditions the pink color of 1.Al³⁺ complex was retained.     

Synthesis,characterization and corrosion inhibition in acid medium of l‐histidine Schiff base complexes

Complexes of cobalt(II), nickel(II) and copper(II) of l ‐histidine Schiff base derived from 2,4‐dihydroxybenzaldehyde and 2‐hydroxy‐1‐naphthaldehyde have been synthesized. The structures of ligands and complexes have been characterized using elemental analysis, molar conductance, magnetic moment measurements, and spectral and thermal studies. The ligands behave as tridentate, coordinating through the azomethine nitrogen and α‐hydroxyl and carboxylic oxygen atoms. The obtained results show that the Cu(II) complexes have square planar geometry, the Co(II) complexes have octahedral and tetrahedral geometries and the Ni(II) complexes have square planar and octahedral geometries. The molecular geometries of the metal complexes are supported by three‐dimensional molecular modelling using molecular mechanics (MM+) and semiempirical molecular orbital calculations (PM3). The inhibition effect of ligands and complexes on the corrosion of aluminium in 2 M H₂SO₄ was investigated using weight loss. The inhibition efficiency is found to increase with increasing inhibitor concentration and temperature. The increase in inhibition efficiency with increasing temperature is suggestive of a chemical adsorption process. Copyright © 2014 John Wiley & Sons, Ltd.     

Selective recognition of Fe3+ and Cr3+ in aqueous medium via fluorescence quenching of graphene quantum dots

Graphene quantum dots (GQDs) have been prepared from graphene oxide (GO) and characterized by standard analytical techniques. The size of the prepared GQDs ranges from 2-10?nm. Aqueous dispersion of GQDs exhibited excitation-dependent emission behavior. Emission intensity of the aqueous dispersion found stable for the examined duration of about four months. GQDs exhibited selective recognition of Fe³⁺ and Cr³⁺ out of various common ions such as alkali, alkaline-earth and transition metal ions in aqueous medium through fluorescence quenching. The lower limit of detection of Fe³⁺ is 1?µM and that of Cr³⁺ is 4?µM.     

Deciphering the bonding mode of the trihalide ligands in a series of halogen carrier homo- and hetero-trihalide Cu(II) Schiff base complexes

Electronic structure calculation techniques (DFT) have been used to decipher the bonding of the trihalide ligands in a series of homo- and hetero-trihalide Cu(II) Schiff base complexes formulated as [Cu(RdienR)(X)(XY₂)] (RdienR = Schiff base; R = furan, thiophene or pyrrol; X = Cl or Br; Y = Cl, Br or I). The association of the incoming Y₂ halogen molecule with one of the halide X ligands of the precursor [Cu(RdienR)(X)₂] complexes alters their distorted trigonal bipyramidal stereochemistry which is transformed to a distorted square pyramidal geometry. The bonding mechanism between the halogen Y₂ molecule and the halide X ligand was thoroughly explored by means of various electronic parameters and charge decomposition analysis techniques. The bond dissociation energy of the Cu–XY₂ bond, BDECu–XY₂${\text{BDE}}_{\text{Cu}''–''{\text{XY}}_2}$, was estimated in the range of 61.9–68.4 kcal/mol, while the bond dissociation energy of the X–Y₂ bond, BDECu–XY₂${\text{BDE}}_{\text{Cu}''–''{\text{XY}}_2}$, was found in the range of 10.6–12.5 kcal/mol. It was found that the X?Y₂ interactions correspond to weak hyperconjugative donor–acceptor interactions between a non-bonding n(X) molecular orbital (donor orbital) localized on the coordinated halide X ligand and an antibonding σ^∗(Y–Y) molecular orbital (acceptor orbital) localized on the Y₂ halogen molecule. The n(X) → σ^∗(Y–Y) donor–acceptor interactions are associated with a second-order perturbation stabilization energy, ΔE(2) of 34.5–52.5 kcal/mol. The loose association of the halogen molecules with the coordinated halide ligand renders the [Cu(RdienR)(X)(XY₂)] complexes good halogen carrier molecules.     

Synthesis,characterization, biological activity,and corrosion inhibition in acid medium of unsymmetrical tetradentate N2O2 Schiff base complexes

Four divalent metal(II) complexes, namely [Co(II)L(H₂O)Cl]·2H₂O, [Ni(II)L(H₂O)Cl]·4H₂O, [Cu(II)L(H₂O)Cl]·3H₂O, and [Zn(II)L(H₂O)Cl]·5H₂O, {L = 2‐furan‐2‐ylmethyleneamino‐phenyl‐iminomethylphenol}, were synthesized and characterized by several techniques. The molar conductance measurement of all analyzed complexes in DMSO showed their non‐electrolytic nature. The new Schiff base ligand (HL) acts as tetradentate ligand, coordinated through deprotonated phenolic oxygen, furan ring oxygen, and two azomethine nitrogen atoms. The ligand field parameters were measured for the metal complexes, which were found to be in the range notified for an octahedral structure. The molecular structural parameters of the synthesized HL ligand and its related metal(II) complexes were calculated and correlated with the experimental parameters such as infrared (IR) data. The investigated ligand and metal complexes were screened for their in vitro antimicrobial activities against different types of fungal and bacterial strains. The resulting data confirmed the examined compounds as a highly promising bactericides and fungicides. The antitumor activities of all inspected compounds were evaluated against colon carcinoma (HCT‐116) and mouse myelogenous leukemia carcinoma (M‐NFS‐60) cell lines. The inhibition effect of HL ligand and its isolated complexes on the corrosion carbon in the form of a rod of area 0.35 cm² in HCl was investigated by measuring the weight loss at 25 °C.     

A novel and synthetically facile coumarin-thiophene-derived Schiff base for selective fluorescent detection of cyanide anions in aqueous solution: Synthesis,anion interactions,theoretical study and DNA-binding properties

A colorimetric and fluorescent chemosensor (chemosensor 2) for the detection of cyanide anions in aqueous solution has been designed and synthesized in high yield. The sensing mechanism of the chemosensor was verified via UV–vis, fluorimetric, and NMR titrations, and was theoretically explained using DFT and TD-DFT calculations. The chemosensor could optically discriminate the presence of fluoride ions over other anions by a color change from yellow to red with an enhancement of pink fluorescence in DMSO. However, it showed strong green fluorescence when CN^? was added to a mixture of DMSO/water (6:4 v/v). Thus, the chemosensor can be employed in selective detecting of CN^? besides other interference anions (F^?, AcO^? and H₂PO₄^?) in aqueous solution. Moreover, 2 can be used to detect CN^? at a concentration as low as 0.32?μM, which is lower than the WHO guideline (2.7?μM) for cyanide. A low quantity of CN^? (1.08?μM) can be detected and quantified using the prepared chemosensor. Moreover, the UV–vis and fluorescence spectroscopy studies of the interactions between 2 and dublex DNA revealed intercalative binding of calf thymus DNA to the chemosensor.     

Vibrational spectra and structures of urazole and 4-methylurazole: DFT calculations of the normal modes in aqueous solution and in the solid state,and the influence of hydrogen bonding

Solid-state IR and Raman as well as aqueous solution state Raman spectra are reported for urazole, 4-methylurazole and their deuterated derivatives. DFT calculations, at the B3-LYP/cc-pVTZ level, established that the structures and vibrational spectra of the molecules can be interpreted using models with hydrogen-bonded water molecules, in conjunction with the polarizable continuum solvation method. The vibrational spectra were computed at the optimised molecular geometry in each case, enabling normal coordinate analysis, which yielded satisfactory agreement with the experimental IR and Raman data. Computed potential energy distributions of the normal modes provided detailed vibrational assignments. Solid-state pseudopotential-plane-wave DFT calculations, using the PW91 functional were also carried out, reflecting the importance of intermolecular hydrogen bonding in the solid state.     

Synthesis and fluorescence study of the grafted salicylidene Schiff base onto SBA-15 mesoporous silica for detecting Zn<Superscript>2+</Superscript> traces in aqueous medium

A selective fluorescent chemosensor was prepared by anchoring pyridine-2-carbaldehyde Schiff base ligand onto mesochannels of organically modified SBA-15 mesoporous silica. The resulting organic-inorganic hybrid mesoporous chemosensor was characterized by X-ray diffraction, Fourier transform IR spectroscopy, transmission electron microscopy, UV-visible diffuse reflectance spectra, and photoluminescence spectra. All the results support the idea that successive attachment of the ligand moiety onto one-pot-modified mesoporous scaffold has not altered its basic hexagonally arranged structure. Upon introducing trace amounts of zinc ions into aqueous solution, remarkable enhancement in the fluorescence was observed.     

A simple and clean procedure for the synthesis of polyhydroacridine and quinoline derivatives: reaction of Schiff base with 1,3-dicarbonyl compounds in aqueous medium

A clean and simple synthesis of benzo[c]acridine, benzo[a]acridine, pyrido[2,3-c]acridine and benzo[f]quinoline derivatives was accomplished in good to excellent yields via the reaction of Schiff base with 1,3-dicarbonyl compounds in aqueous medium catalyzed by TEBA. The structures were characterized by ¹H NMR, IR and elemental analysis, and confirmed by X-ray diffraction study.     

Synthesis of di‐nitrogen Schiff base complexes of methyltrioxorhenium(VII) and their application in epoxidation with aqueous hydrogen peroxide as oxidant

Several di‐nitrogen Schiff bases were synthesized through the condensation of 2‐pyridinecarboxaldehyde with primary amines. The Schiff bases as ligands coordinated with methyltrioxorhenium (MTO) smoothly to afford the correspondent complexes which were characterized by IR, ¹H NMR, ¹³C NMR, MS and elemental analysis. One of the complexes was analyzed by X‐ray crystallography as well. The results revealed that the complexes display distorted octahedral geometry in the solid state with a trans‐position of Schiff base. Catalytic results indicated that the complexes as catalysts increased the selectivity of epoxides remarkably compared with MTO in the epoxidation of alkenes with 30% hydrogen peroxide as oxidant and the increasing rate depended on the structure of the Schiff base ligands of the complexes. The results indicated that the stronger the donating ability of the ligand, the higher selectivity of epoxides the complex gave in the epoxidation of alkenes with 30% hydrogen peroxide as oxidant. Copyright © 2010 John Wiley & Sons, Ltd.     

一例喹喔啉酰腙荧光探针对锌离子的选择性高灵敏识别及细胞成像应用

通过缩合反应制备了一例席夫碱荧光探针2-喹喔啉甲醛缩2-吡啶酰肼(1),使用核磁共振氢谱和碳谱及质谱等手段表征了探针的结构。荧光光谱分析表明,探针1自身无荧光,而Zn²⁺能够导致其在500 nm处出现强发射峰。该荧光增强能够在常见阳离子中选择性检测 Zn²⁺,检测限低至 0.16 μmol·L^-1。通过核磁、质谱和紫外等手段推测了探针 1与 Zn²⁺可能的配位模式。通过单晶X射线衍射解析了1-Zn²⁺配合物的晶体结构,进一步确认了探针的配位行为。1-Zn²⁺晶体中探针分别采取ONN和NN配位模式螯合2个Zn²⁺,并由桥联CH₃O^-和Cl^-连接形成一维链状结构。此外,该探针还可用于活细胞中Zn²⁺的检测。     

一例喹喔啉酰腙荧光探针对锌离子的选择性高灵敏识别及细胞成像应用

通过缩合反应制备了一例席夫碱荧光探针2-喹喔啉甲醛缩2-吡啶酰肼(1),使用核磁共振氢谱和碳谱及质谱等手段表征了探针的结构。荧光光谱分析表明,探针1自身无荧光,而Zn²⁺能够导致其在500 nm处出现强发射峰。该荧光增强能够在常见阳离子中选择性检测Zn²⁺,检测限低至0.16μmol·L^-1。通过核磁、质谱和紫外等手段推测了探针1与Zn²⁺可能的配位模式。通过单晶X射线衍射解析了1-Zn²⁺配合物的晶体结构,进一步确认了探针的配位行为。1-Zn²⁺晶体中探针分别采取ONN和NN配位模式螯合2个Zn²⁺,并由桥联CH₃O^-和Cl^-连接形成一维链状结构。此外,该探针还可用于活细胞中Zn²⁺的检测。     

Charge‐assisted hydrogen bonding in salts of 2‐amino‐1H‐benzimidazole with 3‐phenylpropynoic acid and oct‐2‐ynoic acid

The 100 K structures of two salts, namely 2‐amino‐1H‐benzimidazolium 3‐phenylpropynoate, C₇H₈N₃⁺·C₉H₅O₂⁻, (I), and 2‐amino‐1H‐benzimidazolium oct‐2‐ynoate, C₇H₈N₃⁺·C₈H₁₁O₂⁻, (II), both have monoclinic symmetry (space group P2₁/c) and display N—H...O hydrogen bonding. Both structures show packing with corrugated sheets of hydrogen‐bonded molecules lying parallel to the [001] direction. Two hydrogen‐bonded ring motifs can be identified and described with graph sets R²₂(8) and R⁴₄(16), respectively, in both (I) and (II). Computational chemistry calculations performed on both compounds show that the hydrogen‐bonded ion pairs are more energetically favourable in the crystal structure than their hydrogen–bonded neutral molecule counterparts.